Game depth is decided on a couple factors. I look at the length of a game, the difficulty learning a game, and the game play experience.
I look at length because for some players, after some time the game begins to turn jarring making choices and actions more difficult with the growing signs of impatience. This can make a game seem harder than it is.
I look at difficulty of learning a game because lighter game players either wont understand some of the mechanics or game play strategies OR it may simply not be in their taste to play something with this much to take on.
Finally, I look at game play experience. This is a simple one–those who enjoy Codenames may not want to jump onto scythe right away without some gateway games to grow some board game mechanic knowledge.